Debate Heats Up On Role Of Climate In Human Evolution

TERRADAILY

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Boulder - Oct 29, 2003
Scientists at the Geological Society of America annual meeting in Seattle next week are taking a comprehensive new look at drivers of human evolution. It now appears that climate variability during the Plio-Pleistocene (approximately 6 million years in duration) played a hugely important role.

Astronomically controlled climate forcing on scales ranging from 20,000 to 100,000 years down to El Niños (5-7 years) made a highly unpredictable environment in which generalists with intelligence, language, and creativity were best able to adapt.

Traditional studies of human evolution have focused largely on finding and dating hominid fossils. Today the investigation is rapidly expanding with advances in DNA research and understanding of global climate change. The combination of archeological, geologic, and paleoclimatic evidence allows scientists to explore such tantalizing questions as:

What were the drivers that may have nudged hominids toward bi-pedalism?

Why did only one species ultimately succeed at it?

How might global climate change have influenced brain development, development of tools, and the exodus from Africa?

How did glacial periods in Europe, Asia, and North America impact humans?

"The answers to these questions will not all come from the bones, but from what was taking place in the environment in which they were found," says Gail Ashley, Dept. of Geological Sciences, Rutgers University.

Ashley and Craig Feibel of Rutgers have assembled an interdisciplinary group of distinguished scientists � physical anthropologists, archaeologists, geologists, and paleoclimatologists � for a Pardee Keynote Symposia, The Paleoenvironmental and Paleoclimatic Framework of Human Evolution. The symposium takes place at GSA on Monday, Nov. 3.

- William Ruddiman, celebrated author of Earth's Climate: Past and Future, provides an overview of climate change over the last several million years, helping to separate fact from fiction.

- Bernard Wood, a world-renowned physical anthropologist, discusses the hominin family "Tree of Life" and the challenges of working with the meager fossil record of human evolution spanning the last 7 million years.

- Thure Cerling is a pioneer in using isotope records of bones and teeth. With co-authors Meave Leakey and John Harris he provides a comprehensive look at the impact of climate change on the biological record from one of richest fossil sites in the world (Lake Tukana, Kenya).

- Jonathan Wynn unravels some of the paleoclimate puzzles from fossil soils at key sites in the "Cradle of Mankind" in East Africa. The soils provide clear documentation of extremely arid events. Prolonged droughts may have been a factor in triggering migrations of hominins out of Africa.

- Julia Lee-Thorpe, a trail blazing geochemist, has taken a more personal approach to human evolution by examining hominin nutrition through analyses of tooth enamel. Diet is a direct record of available food resources and an indirect record of the environment in which the individual lived.

- Andrew Hill, a globally recognized expert on the paleontological record in East Africa, reports on the latest findings from the superb paleoenvironmental record of the Tugen Hills, Kenya (site of the discovery of the 6 million-year-old "Millennium Man").

- Gail Ashley speculates on the critical role of the availability of water in affecting human evolution, based on studies from Olduvai Gorge and other fossil localities. Dramatic fluctuations in climate (wet to dry) in East Africa may have been an important factor in affecting natural selection of species able to cope through arid periods.

- David Lordkipanidze and Reid Ferring tell an exciting chapter on the "Out-of-Africa" story from Dmanisi, Republic of Georgia. The 1.8 million-year-old hominin remains are the first discoveries outside Africa to show clear affinities to early African Homo.

- Rick Potts, author of the provocative book Humanity's Descent: The Consequences of Ecological Instability, contributes important new findings from China revealing the successful adaption of some hominin groups 400,000 years ago to climatic fluctuations and drastic environmental change.

- James Dixon, a recognized authority on peopling of the Americas, provides the most recent chapter in the record of humans. Continental ice sheets, sea level changes and the presence of the Bering land bridge effectively controlled immigration from Asia to the New World.

- Craig Feibel provides perspective on the physical environmental constraints in which human evolution took place. He examines the role of geologic factors such as plate tectonics, sea level change, and climate fluctuations in affecting selective pressure on hominins and thereby impacting how and where humans evolved.

TERRADAILY

DNA Fragments Help Trace Migration Routes Of Modern Humans

Stanford - May 28, 2003
Human beings may have made their first journey out of Africa as recently as 70,000 years ago, according to a new study by geneticists from Stanford University and the Russian Academy of Sciences.

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